1. Field of the Invention
The present invention relates to an actuator driven by step advance, a method of driving the actuator, and an actuator system including such an actuator.
2. Description of the Related Art
A digital camera is incorporated in a cellular phone or personal digital assistant, and an image taking optical module is demanded to be much smaller in size. Accordingly, in place of a conventional electromagnetic actuator, an electrostatic actuator is proposed.
For example, Jpn. Pat. Appln. KOKAI Publication No. 5-26149 proposes an object driving apparatus comprising a first contact part having first static electricity applying means connected to a first conductor thereof, and configured so that a first dielectric element covering the surface of the first conductor contacts with the contact surface, a second contact part having second static electricity applying means connected to a second conductor thereof, and configured so that a second dielectric element covering the surface of the second conductor contacts with the contact surface, and an expandable material for coupling the first conductor and second conductor. In synchronism with expansion and contraction of the expandable material, the first static electricity applying means and second static electricity applying means invert to each other so as to be capable of moving substantially in the horizontal direction to the contact surface. That is, this Jpn. Pat. Appln. KOKAI Publication No. 5-26149 discloses a configuration of forming a contact part of large frictional force and a contact part of small force intentionally, coupling them with an expandable material, and moving the two contact parts in the same direction by inverting the magnitude relation of the frictional force in synchronism with expansion and contraction of the expandable material.
Further, Jpn. Pat. Appln. KOKAI Publication No. 2000-253683 discloses an inchworm mechanism comprising a support element, a mobile element capable of relatively moving on the support element, a driving element existing at a position close to the mobile element, expanding means for displacing the driving element relatively to the support element, and an electrostatic clamping mechanism for clamping and driving the mobile element and driving element.